A symptom-limited incremental cycling exercise test will be performed at week 0 to rule out the presence of cardiovascular co-morbidities. Subjects will be seated on an electromagnetically braked cycle ergometer (Ergoselect 200P, Ergoline, Germany) and connected to a cardio-respiratory circuit through a mouthpiece (Jaeger Oxycon Pro, CareFusion, Germany). After 3min of unloaded pedalling, the workload will be increased in a stepwise manner up to the individual's maximal capacity. Each step will last 1min and increments of 5-10W will be used. Gas exchange parameters and HR will be measured at rest and during exercise on a breath-by-breath basis. The ventilatory threshold will be determined using the V-slope method, a computerized approach to identify the breakpoint in the carbon dioxide output-oxygen uptake relationship. Peak work rate will be defined as the highest work rate maintained at a pedalling speed of at least 50rpm for a minimum of 30sec.